Numeric contexts

This is the context when using an arithmetical operator.

In this context if either operand is a float (or not interpretable as an int), both operands are interpreted as floats, and the result will be a float. Otherwise, the operands will be interpreted as ints, and the result will also be an int. As of PHP 8.0.0, if one of the operands cannot be interpreted a TypeError is thrown.

String contexts

This is the context when using echo, print, string interpolation, or the string concatenation operator.

In this context the value will be interpreted as string. If the value cannot be interpreted a TypeError is thrown. Prior to PHP 7.4.0, an E_RECOVERABLE_ERROR was raised.

Logical contexts

This is the context when using conditional statements, the ternary operator, or a logical operator.

In this context the value will be interpreted as bool.

Integral and string contexts

This is the context when using bitwise operators.

In this context if all operands are of type string the result will also be a string. Otherwise, the operands will be interpreted as ints, and the result will also be an int. As of PHP 8.0.0, if one of the operands cannot be interpreted a TypeError is thrown.

Comparative contexts

This is the context when using a comparison operator.

The type conversions which occur in this context are explained in the Comparison with Various Types table.

Function contexts

This is the context when a value is passed to a typed parameter, property, or returned from a function which declares a return type.

In this context the value must be a value of the type. Two exceptions exist, the first one is: if the value is of type int and the declared type is float, then the integer is converted to a floating point number. The second one is: if the declared type is a scalar type, the value is convertable to a scalar type, and the coercive typing mode is active (the default), the value may be converted to an accepted scalar value. See below for a description of this behaviour.

<?php
// int|string
42    --> 42          // exact type
"42"  --> "42"        // exact type
new ObjectWithToString --> "Result of __toString()"
                      // object never compatible with int, fall back to string
42.0  --> 42          // float compatible with int
42.1  --> 42          // float compatible with int
1e100 --> "1.0E+100"  // float too large for int type, fall back to string
INF   --> "INF"       // float too large for int type, fall back to string
true  --> 1           // bool compatible with int
[]    --> TypeError   // array not compatible with int or string

// int|float|bool
"45"    --> 45        // int numeric string
"45.0"  --> 45.0      // float numeric string

"45X"   --> true      // not numeric string, fall back to bool
""      --> false     // not numeric string, fall back to bool
"X"     --> true      // not numeric string, fall back to bool
[]      --> TypeError // array not compatible with int, float or bool
?>

Type Casting

Type casting converts the value to a chosen type by writing the type within parentheses before the value to convert.

<?php
$foo = 10;   // $foo is an integer
$bar = (bool) $foo;   // $bar is a boolean
?>

The casts allowed are:

• (int) - cast to int
• (bool) - cast to bool
• (float) - cast to float
• (string) - cast to string
• (array) - cast to array
• (object) - cast to object
• (unset) - cast to NULL

Note:

(integer) is an alias of the (int) cast. (boolean) is an alias of the (bool) cast. (binary) is an alias of the (string) cast. (double) and (real) are aliases of the (float) cast. These casts do not use the canonical type name and are not recommended.

Note:

Whitespaces are ignored within the parentheses of a cast. Therefore, the following two casts are equivalent:

<?php
$foo = (int) $bar;
$foo = ( int ) $bar;
?>

<?php
$binary = (binary) $string;
$binary = b"binary string";
?>

Note: Instead of casting a variable to a string, it is also possible to enclose the variable in double quotes.

<?php
$foo = 10;            // $foo is an integer
$str = "$foo";        // $str is a string
$fst = (string) $foo; // $fst is also a string

// This prints out that "they are the same"
if ($fst === $str) {
    echo "they are the same";
}
?>

It may not be obvious exactly what will happen when casting between certain types. For more information, see these sections:

• Converting to boolean
• Converting to integer
• Converting to float
• Converting to string
• Converting to array
• Converting to object
• Converting to resource
• Converting to NULL
• The type comparison tables

Note: Because PHP supports indexing into strings via offsets using the same syntax as array indexing, the following example holds true for all PHP versions:

<?php
$a    = 'car'; // $a is a string
$a[0] = 'b';   // $a is still a string
echo $a;       // bar
?>

See the section titled String access by character for more information.